Published: November 2006
Did You Know?
In Did You Know? the National Geographic magazine team shares extra information we gathered to expand your knowledge of our featured subjects.

The red-eyed tree frog, whose embryos can hatch early if they detect a predatory threat, isn't the only species that can grow up in a hurry when survival demands it. Scientists have discovered evidence of such life-stage plasticity among a variety of species.

Both flathead minnows and southern leopard frogs hatch more quickly when threatened by certain crayfish. And some leeches are known to send the embryos of Pacific tree frogs and Cascades frogs squirming away ahead of schedule. Experts think chemical cues from predators or from injured eggs may be signals for early hatching.

Pale spitting spiders, whose females carry eggs on their backs rather than leaving them in unprotected clumps, can also accelerate hatching when jumping spiders attack. By lightening the mother spider's load, early hatching may help spare both the embryos and the parent from danger.

—Brad Scriber